Many optical printers use a laser scanning process. The intensity of a laser light beam focused on a two-dimensional photosensitive surface is modulated as the beam is moved relative to such surface to provide a two-dimensional output image at an image zone. In one common system, a constantly rotating multi-faceted polygon is used to line scan a beam of light from the laser across a photosensitive member at the image zone. An acoustooptic modulator intensity modulates the beam in accordance with the gray or brightness level of pixels of a digital image held in a frame store memory. The rotating polygon has the advantages of high generation rates, high resolution and relatively maintenance-free operation.
Prior laser printers usually print only one format size. See for example, U.S. Pat. Nos. 4,040,096 and 4,247,160. These laser printers employ a constantly rotating polygon scanner which scans a fixed line length and uses a fixed number of pixels. In order to change format size, the print must be capable of changing spot size at the image zone, line scan length and page length and these features are costly and difficult to implement in any one printer. Commonly assigned U.S. application Ser. No. 719,092 entitled "Multi-Format Printer" to Chandler et al filed 4-2-85, discloses an effective multi-format polygon laser printer which scans a beam across an image zone. This printer changes image format size. Each time the format size is changed, changes are made to the beam spot size. More particularly, a cylindrical mirror is moved to change the line scan length. The velocity of the photosensitive member is adjusted to change the page scan length.